Two different types of medical therapy for the symptoms of benign prostatic hyperplasia (BPH) now have been approved by the U.S. Food and Drug Administration. The first was finasteride, a 5-alpha reductase inhibitor; the other was terazosin, a selective alpha-1-adrenergic receptor inhibitor. Both of these drugs as well as other alpha blockers, such as doxazosin and prazosin, now are being used widely in the United States and around the world, both by urologists and primary care physicians, to treat the symptoms of prostatism. However, it is not known whether treatment with these agents will reduce or prevent the clinical progression of BPH when these medications are taken chronically. Clinically important BPH endpoints include acute urinary retention, increasing renal failure, severe bladder decompensation with chronic retention and incontinence, recurrent urinary tract infections and progressive voiding symptoms requiring surgical intervention. The Urology and Clinical Trials Program of the NIH NIDDK appropriately has developed a prospective randomized clinical research study investigating the long- term medical therapy of BPH using finasteride, doxazosin, the combination of finasteride and doxazosin, and a placebo arm. With this application, clinical research personnel from the Mayo Clinic Department of Urology (Rochester, Minnesota) are applying to be one of the "Clinical Centers" as described in the new RFA. Our research group seeks to further utilize talent and experience generated over the preceding six years by Mayo personnel prospectively studying men with BPH. We already have had extensive experience in conducting multi-center prospective clinical trials investigating the natural history of BPH without treatment, and also in numerous multi-center prospective randomized industry sponsored clinical trials investigating finasteride, alpha- blockers and new devices for BPH. Our clinical research team also has had current experience in enrolling over 400 middle-aged male patients in the past eight months for the new NCI-SWOG chemoprevention trial of prostate cancer (PCPT) which has finasteride and placebo arms and which has many similarities to the proposed NIDDK BPH study in terms of overall organization of the multi-center trial and duration. We believe the ability and experience of the Mayo Clinic Department of Urology clinical investigation team in carrying out prospective trials of prostate disease should make us a strong candidate to become one of the clinical centers as described in the current NIDDK RFA.